214 Dr Hibbert on the Limestone of Burdiehouse, 



the neighbourhood of Glasgow, and in the districts of Cupar, 

 Errol in Perthshire, East Calder, and Musselburgh ; also in the 

 coal-fields of Northumberland, of Yorkshire, and of North Wales. 

 It amounts only to a probability, that remains of the Megalich- 

 thys have been found in certain limestones of Ashford, in Derby- 

 shire, and of Northumberland. The details of these discoveries 

 are given in the note appended to this section. 



M. Agassiz has stated his opinion, that there exists in Scot- 

 land another species of Megalichthys, of which some relics were 

 placed in his hands by Mr Robison, who had procured them 

 from Greenside near Glasgow. He conceives that the animal to 

 which they may be referred, is to be distinguished from that of 

 Burdiehouse by the form of the teeth, which is more compressed 

 and very sharp at the edges. He proposes to call it the Mega- 

 lichthys falcatus. 



NOTES TO SECTION XII. 



If it be allowable to suspect that the scales of the Megalichthys have been mis- 

 taken for those of saurian reptiles, as was the case in the first instance at Burdie- 

 house, the evidence with regard to other localities in which the remains of the Mega- 

 lichthys have been found, becomes multiplied. 



The black limestone, as it is called, of Ashford in Derbyshire, so named from 

 the bituminous matter which is diffused through a great part of it, rather affords 

 evidence of its having been the deposit of an estuary than of a fresh water river, 

 or lake, such as the limestone of Burdiehouse is supposed to have been. This fact I 

 shall endeavour to substantiate hereafter. It is sufficient at present to state, that 

 the limestone of Ashford contains, along with marine shells and corallines, various 

 remains of the plants common in coal-fields. 



In this limestone Mr Whitehurst, who wrote his well known Theory of the 

 globe in the year 1778, found, as he stated, the impression of a crocodile. Mr 

 White Watson of Bakewell conceives that Mr Whitehurst mistook for these re- 

 mains a large orthoceratite ; but, with all due deference to my old acquaintance, I 

 am inclined to doubt the legitimacy of this explanation, from having myself lately as- 

 certained that remains of very large fish existed in this limestone, which, if not of the 

 Megalichthys, assimilated themselves to other remains found at Burdiehouse ; — this 

 being a fact which had been previously unknown. It seems then at least a plausible 

 conjecture, that some remains of a large sauroid fish might have turned up in this 

 locality. 



This suspicion meets with additional support from a passage which we find in 



